(a) Describe the bonding in the M₂ diatomics (M = Li, Na, K, Rb, Cs) in terms of valence bond and molecular orbital theories. 

(b) Account for the trend in metal–metal bond dissociation energies given in Table 11.1.

Transcribed Image Text:

Table 11.1 Some physical properties of the alkali metals, M, and their ions, Mt. Property Atomic number, Z Ground state electronic configuration [He]2s¹ 161 Enthalpy of atomization, AH°(298 K)/kJ mol-¹ Dissociation enthalpy of M-M bond in M₂ (298 K)/kJ mol-¹ Melting point, mp/K Li Boiling point, bp/K Standard enthalpy of fusion, Afus H (mp)/kJ mol-¹ 3 110 453.5 1615 3.0 Na 11 [Ne]3s¹ 108 74 371 1156 2.6 K 19 [Ar]4s¹ 90 55 336 1032 2.3 Rb 37 [Kr]5s¹ 82 49 312 959 2.2 Cs 55 [Xe]6s¹ 78 44 301.5 942 2.1